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How to change the background color of a view from a different activity in android?

I am working on a Quiz app. First when a user opens the app they go to the MainActivity, from there when they press start they go to the Categories Activity , from there after selecting a category they go to the Sets Activity, from there after selecting a set the go to the Questions Activity and finally after completing all the questions they reach the Score Activity. Here in the score activity when the click on Done button they are redirected to the MainActivity. In the Score Activity i want to change the color of the Set that they completed to green instead of the default color. How can i do this? I created a sets item layout xml file and used an adapter to fill the gridview in the Sets Activity with views from the adapter. Currently i am getting a null object reference after clicking the Done button in the ScoreActivity.
Here is the code :
SetsAdapter.java
public class SetsAdapter extends BaseAdapter {
private int numOfSets;
public SetsAdapter(int numOfSets) {
this.numOfSets = numOfSets;
}
#Override
public int getCount() {
return numOfSets;
}
#Override
public Object getItem(int position) {
return null;
}
#Override
public long getItemId(int position) {
return 0;
}
#Override
public View getView(final int position, View convertView, final ViewGroup parent) {
View view;
if(convertView == null){
view = LayoutInflater.from(parent.getContext()).inflate(R.layout.set_item_layout, parent, false);
}
else {
view = convertView;
}
view.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent questionIntent = new Intent(parent.getContext(), QuestionActivity.class);
questionIntent.putExtra("SETNUM", position +1);
parent.getContext().startActivity(questionIntent);
}
});
((TextView) view.findViewById(R.id.setNumber)).setText(String.valueOf(position+1));
return view;
}
}
SetsActivity.java
public class SetsActivity extends AppCompatActivity {
private GridView sets_grid;
private FirebaseFirestore firestore;
public static int categoryID;
private Dialog loadingDialog;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sets);
Toolbar toolbar = (Toolbar)findViewById(R.id.set_toolbar);
setSupportActionBar(toolbar);
String title = getIntent().getStringExtra("CATEGORY");
categoryID = getIntent().getIntExtra("CATEGORY_ID",1);
getSupportActionBar().setTitle(title);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
sets_grid = findViewById(R.id.sets_gridView);
loadingDialog = new Dialog(SetsActivity.this);
loadingDialog.setContentView(R.layout.loading_progressbar);
loadingDialog.setCancelable(false);
loadingDialog.getWindow().setBackgroundDrawableResource(R.drawable.progress_background);
loadingDialog.getWindow().setLayout(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
loadingDialog.show();
firestore = FirebaseFirestore.getInstance();
loadSets();
}
private void loadSets() {
firestore.collection("Quiz").document("CAT" + String.valueOf(categoryID))
.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
#Override
public void onComplete(#NonNull Task<DocumentSnapshot> task) {
if (task.isSuccessful()) {
DocumentSnapshot doc = task.getResult();
if (doc.exists()) {
long sets = (long) doc.get("SETS");
SetsAdapter adapter = new SetsAdapter(Integer.valueOf((int)sets));
sets_grid.setAdapter(adapter);
} else {
Toast.makeText(SetsActivity.this, "No Sets Exists!", Toast.LENGTH_SHORT).show();
finish();
}
} else {
Toast.makeText(SetsActivity.this, task.getException().getMessage(), Toast.LENGTH_SHORT).show();
}
loadingDialog.cancel();
}
});
}
#Override
public boolean onOptionsItemSelected(#NonNull MenuItem item) {
if(item.getItemId() == android.R.id.home)
finish();
return super.onOptionsItemSelected(item);
}
}
ScoreActivity.java
public class ScoreActivity extends AppCompatActivity {
private TextView score;
private Button done;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_score);
score = findViewById(R.id.score_tv);
done = findViewById(R.id.score_activity_done);
String score_str = getIntent().getStringExtra("SCORE");
final int setNum = getIntent().getIntExtra("SetNum", 1);
score.setText(score_str);
done.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// Here is the issue I am facing
View view = findViewById(R.id.setNumber);
view.setBackgroundColor(Color.GREEN);
Intent mainIntent = new Intent(ScoreActivity.this, MainActivity.class);
startActivity(mainIntent);
ScoreActivity.this.finish();
}
});
}
}

As your activity Sequence is MainActivity -> Categories -> Sets -> Scores.
You've two options to change the color with two different life cycle of the change.
To change the color on a temporary basis, this will reset itself after closing the app or resrtating the 'Sets' activity. It can be done in two ways: Using Public Static Variable and using a public function.
To change the color on a permanent basis until the app is uninstalled/reinstalled. You should use SharedPreferences. SharedPreferences acts like a private data stored in device's memory for further use and it stays there unchanged until and unless the app is removed/data is cleared. Although, apps with root permission can access any app's SharedPreferences data and can modify it as well.You can use SharedPreferences as explained here. Or, you can use some library to access it an easy way. The way I use it in all my apps is TinyDB(it's just a java/kotlin file). This works as:
//store the value from ScoreActivity after completion as
TinyDB tinyDB = TinyDB(this);
tinyDB.putBoolean("isSet1Completed",true);
//access the boolean variable in SetsActivity to change the color of any set that
//is completed and if it's true, just change the color.
TinyDB tinyDB = TinyDB(this);
Boolean bool1 = tinyDB.getBoolean("isSet1Completed");
But, it's your choice what way you want to prefer.
Now, this was about the lifecycle of the change you'll do: Temp or Permanent. Now, we'll talk about how you change the color.
Using public static variable in Sets activity. What you can do is you can set the imageView/textview whose background you want to change as public static variable. Remember, this idea is not preferred as it causes memory leak but it's just easy.
Declare it as public static ImageView imageview;(or TextView) intialize it in the
onCreated() as imageView = finViewById(R.id.viewId); in Sets activity. Call
it as new SetsActivity().imageView.setBackgroundColor(yourColor); in ScoreActivity.
Second way is to create a public function in SetsAcitvity, putting the color change code in it, and then calling it from the ScoreActivity. Just declare it as public void changeColor(){ //your work} and call it from ScoreActivity as new SetsActivity().changeCOlor(). You can also pass some arguments to the function like setId.
I've provided you every thing you need. Rest you should figure out yourself to actually learn it and not copy it.

I think simply you add flag in MainActivity.
for example, add flag in MainActivity.
boolean isFromDone = false;
and when done clicked,
done.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// Here is the issue I am facing
Intent mainIntent = new Intent(ScoreActivity.this, MainActivity.class);
mainIntent.putExtra("FromDone", true);
startActivity(mainIntent);
ScoreActivity.this.finish();
}
});
and in MainActivity, add this.
#Override
protected void onResume() {
super.onResume();
isFromDone = getIntent().getBooleanExtra("FromDone", false);
if(isFromDone) {
(TextView) view.findViewById(R.id.setNumber)).setBackgroundColor(Color.GREEN);
}
}

Suppose you have a Linear Layout in Activity A and you want to change it's background color from a button click which is present in Activity B.
Step 1 Create a class and declare a static variable.
class Util { private static LinearLayout mylayout ; }
Step 2
In the activity which is holding this layout, initialize it.
Util.mylayout = findviewbyid(R.id.linear);
Step 3Change the background color on button click from Activity B
onClick{
Util.mylayout.setBackgroundColor(Color.RED);
}

How to apply search filter to a recyclerview with categorical filtering?

Right now, I have a recyclerview with items of two categories, and three buttons on the activity which filters them by "all", "design category" and "development category". When a button is clicked, only items of that category is displayed. I also have a search bar, which filters the results by name. After something is typed into the searchbar and the results are filtered, if a categorical button is clicked, it displays all items of that category instead of only items that match the name that is searched.
My only current solution is to clear the searchbar when a button is clicked, but I want to make it so that the searchbar filter still applies after a button is clicked.
HomeActivity.Java:
public class HomeActivity implements RecyclerViewAdapter.RecyclerViewOnClickListener{
#Override
protected void onCreate(Bundle savedInstanceState) {
//other stuffs
final Button allLessonsButton = (Button) findViewById(R.id.allLessonsButton);
allLessonsButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
onAllLessonsButtonTapped();
}});
final Button designLessonsButton = (Button) findViewById(R.id.designLessonsButton);
designLessonsButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
onDesignLessonsButtonTapped();
}});
final Button developmentLessonsButton = (Button) findViewById(R.id.developmentLessonsButton);
developmentLessonsButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
onDevelopmentLessonsButtonTapped();
}});
searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
#Override
public boolean onQueryTextSubmit(String query) {
return false;
}
#Override
public boolean onQueryTextChange(String newText) {
adapter.getFilter().filter(newText);
return false;
}
});
}
setupRecyclerView();
}
private void setupRecyclerView() {
lessonRecyclerView = (RecyclerView) findViewById(R.id.lesson_recycler_view);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
lessonRecyclerView.setLayoutManager(linearLayoutManager);
}
private void onAllLessonsButtonTapped() {
currentLessons = allLessons;
adapter = new LessonRecyclerViewAdapter(this, currentLessons, this);
lessonRecyclerView.setAdapter(adapter);
}
private void onDesignLessonsButtonTapped() {
currentLessons = developmentLessons;
adapter = new LessonRecyclerViewAdapter(this, currentLessons, this);
lessonRecyclerView.setAdapter(adapter);
}
private void onDevelopmentLessonsButtonTapped() {
currentLessons = designLessons;
adapter = new LessonRecyclerViewAdapter(this, currentLessons, this);
lessonRecyclerView.setAdapter(adapter);
}

Essentially your users have two different methods to filter the list before displaying them. On one hand, they can choose a category using buttons; or they can type some texts and filter it by searching.
The main problem right now is to discern the two competing methods of filtering. If a user has both clicked a category and typed a query, we don't know which filter method we should respect.
In my opinion, we should always respect the latest action.
One way to solve this problem is, for example, have a variable recording the latest action the user had. Example pseudocode:
bool isSearching = false
when user types something:
isSearching = true
when a category is clicked:
isSearching = false
filtering:
if isSearching then:
filter based on query
else:
filter based on category
You can implement this logic in different events, such as EditText onQueryTextChange or Button onClickListener event.

Global value becomes null in method

I have created a private member of the whole class called Member curMbr;
The activity (rather the fragment, since this is in a frament class) has a listview
with some contributions from members.
I also have a context menu on that list. When clicking on a contribution, I want a (customized) dialog box to show details about the member. (Member ID is part of the contribution objet. )
#Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
Log.d("FRGCOTIZ02", "create ctxt menu");
AdapterView.AdapterContextMenuInfo info = (AdapterView.AdapterContextMenuInfo) menuInfo;
String[] menuItems = getResources().getStringArray(R.array.ar_menu_ctxt_participant);
// Get selected member
Contribution curCotis = (Contribution) (((ListView)v).getItemAtPosition(info.position));
Participant p = new Participant(helper.getDBItem(DBHelper.TABLE_PARTICIPANT,
DBHelper.COL_ID, curCotis.getParticipant()));
curMbr = new Member(helper.getDBItem(DBHelper.TABLE_MEMBER, DBHelper.COL_ID, p.getMember()));
for (int i = 0; i < menuItems.length; i++) {
menu.add(Menu.NONE, i, i, menuItems[i]);
}
Log.d("FRGCOTIZ01", curMbr.getId_());
}
#Override
public boolean onContextItemSelected(MenuItem item) {
return ( applyContextMenuSelection(item) || super.onContextItemSelected(item) );
}
private boolean applyContextMenuSelection(MenuItem item) {
switch (item.getItemId()) {
case 0: // Summary
final Dialog dlg = new Dialog(this.getContext());
final String sessID;
try {
sessID = KUtil.DATE_FORMAT.format(curSess.getDate());
dlg.setContentView(R.layout.alert_show_charges);
Button btnOK = dlg.findViewById(R.id.btn_alertOK);
btnOK.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
setupAlertDialogCharges(dlg, sessID, curMbr.getId_());
}
});
Button btnCancel = dlg.findViewById(R.id.btn_alertCancel);
btnCancel.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
dlg.dismiss();
}
});
dlg.show();
} catch (Exception e){
Log.d("FRAGMENT Contribution", e.getMessage());
}
break;
case 1: // Collect
break;
case 2: // Cancel
break;
default:
break;
}
return true;
}
In method onCreateContextMenu, I can get the member and display his ID.
But in method applyContextMenuSelection, there is an exception, saying the meber is null!
Funny enough there is another variable that I am using in that method, and it works fine. Difference is, that variable has been set at creation of the fragment.
How do I solve this?

I have been studying the code for a while and the only thing I could figure was that the issue is somehow linked to the use of contextmenu. It seems to me that variables are set back to their original when the menu action is supposed to be executed. Again, I am not too sure about that.
So, the only solution I found so far was to keep that vale in a "higher" context:
When I can still read the value,
getActivity().getIntent().putExtra(HomeActivity.ID_ENTRY, curMbr.getId_());
When I want to use it,
final String mbrID = getActivity().getIntent().getStringExtra(HomeActivity.ID_ENTRY);

Permanently save intent from other activity (with two values) to listview

I'm trying to save two values from an activity (where the user can put in two different values, one String value and one integer value) in the listview from another activity. In the first activity, it shows a list with a course and the amount of points for that course in one listview, like this:
Course: English
Points: 4
Now, the problem is, everytime I want to put in another value using the add_course_actitivty, it overwrites the previous value. I've looked at different solutions, like with sharedpreferences (Add items to listview from other activity), but this uses only one value and if I try to work with sharedpreferences, it overwrites the other value in the sharedpreferences, but I want users to add multiple courses and corresponding points. Also on restart, it deletes the values in the listview (I read to prevent this you need to store it in sharedpreferences, but this doesn't work the way I need it to be)
KeuzeActivity.class (shows the listview):
public class KeuzeActivity extends AppCompatActivity {
private FloatingActionButton fab_add;
private String student_naam;
private ListView keuze_list;
boolean wantDelete;
private ArrayAdapter adapter;
private String vak;
private int ec;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_keuze);
// setting title
student_naam = getIntent().getStringExtra("student");
setTitle("Keuzevakken en projecten van " + student_naam);
//initialzing elements
fab_add = (FloatingActionButton)findViewById(R.id.fab_add);
keuze_list = (ListView) findViewById(R.id.keuze_list);
//initializing list
final ArrayList<Course> courseItems = new ArrayList<Course>();
adapter = new ArrayAdapter<Course>(this, android.R.layout.simple_list_item_1, courseItems);
keuze_list.setAdapter(adapter);
// checks if intent has required values, put it in listview
if (getIntent().hasExtra("vak") && getIntent().hasExtra("ec")) {
vak = getIntent().getStringExtra("vak");
ec = getIntent().getIntExtra("ec", ec);
courseItems.add(new Course(vak, ec));
adapter.notifyDataSetChanged();
}
// make fab go to other activity
fab_add.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(KeuzeActivity.this, add_course_activity.class));
}
});
// long press deletes item
keuze_list.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
#Override
public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
showDeleteDialog();
if (wantDelete) {
courseItems.remove(position);
adapter.notifyDataSetChanged();
}
return true;
}
});
}
private void showDeleteDialog() {
AlertDialog.Builder infobuilder = new AlertDialog.Builder(this);
infobuilder.setCancelable(false);
infobuilder.setTitle("Vak/project verwijderen");
infobuilder.setMessage("Weet je zeker dat je het vak of project wilt verwijderen?");
final TextView text = new TextView(this);
// action when pressed OK
infobuilder.setPositiveButton("Ja", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
wantDelete = true;
dialog.cancel();
}
});
infobuilder.setNegativeButton("Nee", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
wantDelete = false;
dialog.cancel();
}
});
infobuilder.show();
}
}
add_course_activity.class (let's users input course and points)
public class add_course_activity extends AppCompatActivity {
private EditText course_edit;
private EditText ec_edit;
private Button save_btn;
private String student_name;
private int ec;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_add_course);
setTitle("Voeg vak of project toe");
final Context context = getApplicationContext();
// initializing elements
course_edit = (EditText) findViewById(R.id.edit_vak);
ec_edit = (EditText) findViewById(R.id.edit_ec);
save_btn = (Button) findViewById(R.id.save_button);
// action on savebutton
save_btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (course_edit.getText().toString().trim().length() > 0 && ec_edit.getText().toString().trim().length() > 0 ) {
ec = Integer.parseInt(ec_edit.getText().toString());
Intent goBack = new Intent(add_course_activity.this, KeuzeActivity.class);
goBack.putExtra("vak", course_edit.getText().toString());
goBack.putExtra("ec", ec);
goBack.putExtra("student", PreferenceManager.getDefaultSharedPreferences(context).getString("student_name", student_name));
startActivity(goBack);
}
else {
Toast.makeText(context, "Voer juiste informatie in!", Toast.LENGTH_SHORT).show();
}
}
});
}
}
Course.java class (getters and setters + with toString method)
public class Course {
private String vak;
private int ec;
public Course(String vak, int ec) {
this.vak = vak;
this.ec = ec;
}
public String getVak() {
return vak;
}
public void setVak(String vak) {
this.vak = vak;
}
public int getEc() {
return ec;
}
public void setEc(int ec) {
this.ec = ec;
}
#Override
public String toString() {
return ("Vak: " + vak + "\n" + "Punten: " + ec);
}
}
Note that my code isn't clean or done, but to get further I need to fix this problem.

You have several way to do it. As other replies have suggested you can use an SQLLite database and add data to a course table and retrieve data from it.
If you find Db approach to complicated/heavy
You could also use SharedPreferences what you need to do is figure a way to store a string that represent a list of course. It is not the best way to approach it but it will work.
Lets say you choose to serialize your Course object with "vac-ec"
Then you just store a serialized list of course. Example "vac1-ec1,vac2-ec2"
When you need to add a course you juste grab the previous string split it to list, append the new course to the list and re-serialize the list to a string to encode it.
Other solution could be to use Realm.

You should used SQLiteDatabase and create a table with valid attributes and insert your new values into them

Okay, now things are clearer. As answered by #Dwijraj, when storing what potentially will be a large set of data, for maximum control it is best to use SQLite.
You can read more about the different Saving Data methods here:
https://developer.android.com/training/basics/data-storage/index.html
SharedPreferences are best used to store small amounts of information, like storing the settings of an application. [Mute] for example. Or a highscore in case of a game.
A Database is a better option when it comes to storing large pieces of data that you will potentially manipulate.
Your data structure can be something like this, Courses table containing Unique_ID , Course Name, Course Level, Course summary.
A table for English for example which will contain
Exams, Scores, Duration.
There are a lot of things you can do.

Try by storing the records in SQLite, and get it when you want to show.
By this, You can have a track of all added items. And you can show the items you want.

get/use radio button value android

I FIGURED OUT WHAT I WAS DOING. I HAD THE VARIABLE NAME IN QUOTES WITH THE REST OF THE URL STRING.
How do you save the value of a Radio button into a variable and use that variable later.
I can see the variable Day_Item in my LogCat and the value is in there but when try using Day_Item later it does not show the valuable.
Below is a section of my code that shows the buttons.
String Day_Item = null;
public class SearchDB extends Activity {
private static final String TAG = "MyApp";
String start_log = "STARTED";
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.search_layout);
final RadioButton radio_monday = (RadioButton) findViewById(R.id.monday);
radio_monday.setOnClickListener(radio_listener);
cityspinner.setOnItemSelectedListener(new OnItemSelectedListener() {
#Override
public void onItemSelected(AdapterView<?> parent, View view, int position,long arg3)
{
int id = parent.getId();
if (spinner2_count2 < spinner2_count1 ) {
spinner2_count2++; }
else
{
String city_spinner_log = "CITY SPINNER";
Log.d(TAG, city_spinner_log);
String item = cityspinner.getSelectedItem().toString();
String nameContentType = "name";
String cityURL = "GetRestaurant.php?day=Day_Item&city=" + item;
Log.d(TAG, cityURL);
String shop_data = DataCall.getJSON(cityURL,nameContentType);
Log.d(TAG, shop_data);
Bundle bundle = new Bundle();
bundle.putString("shopData", shop_data);
Intent myIntent = new Intent(SearchDB.this, ShowRestaurant.class);
myIntent.putExtras(bundle);
startActivityForResult(myIntent, 0);
}
}
}
//ONCLICKLISTENER that saves RADIO value into a variable.
public OnClickListener radio_listener = new OnClickListener() {
public void onClick(View v) {
// Perform action on clicks
RadioButton rb = (RadioButton) v;
Day_Item = (String) rb.getText();
Log.d(TAG,Day_Item);
Toast.makeText(SearchDB.this, Day_Item, Toast.LENGTH_SHORT).show();
}
};
}

You would need a bit more code to get a good solid answer. Such as how is Day_Item allocated? And is it's scope global? Are you calling it from another activity or the one it's allocated within? These are just guesses at this point:
1) Are you sure your onClickListener isn't firing multiple times? Thus setting Day_Item to an undesired text or nothing at all?
2) Rather a question/answer,
"but when try using Day_Item later it does not show the valuable"
I'm assuming this means that it is null? Well if it's being set properly, and then it is being null'd... it either is being explicitly null'd by you somewhere (such as (1)) or else the allocation and scope are the issue area I believe...